I agree. I think that stressing adaptation/improvisation is a major thrust of the rules set. I've had a couple of games where there were objectives that I knew I couldn't accomplish for one reason or another. It forced me to really think about the objectives I could meet, and to focus my play on denying objectives to my opponent, rather than just playing out the strategy I'd thought of when making the list.
On that level, I think it's also realistic. Some armies show up better prepared than others, some have terrain advantages. Sometimes you show up with a knife at a gunfight. But, that's not a guarantee of a loss. Weird stuff happens on the ground. It's one of the things I really like about 40K, as opposed to other model-based strategy games I've played before. I've had random things totally go my way, and not; ditto for opponents. The issue is not whether or not something unexpected takes place; the issue is how you adapt to it and whether or not you can use it to your advantage.
In that, I think 40K's random/entropic elements actually make it much more "real" than any other strategy game I've played. It reflects the reality that you cannot control every element going into a battle, nor can you control everything that happens on the ground.
Seriously, I hope they put in rules for weather.